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DISPLAYING POSTS TAGGED: insects (9)

In Bugs Alive! you can see almost 50 displays of live invertebrates. Most of them from either tropical or arid parts of Australia, illustrating the adaptations needed for living in extreme environments.

So each year, when the weather conditions are right, we head out to the Mallee to boost our stocks of insects and spiders. The best time to visit is on a hot, humid night—which happened last week—just before or just after a thunderstorm. Like most desert species, Mallee insects wait months for the rain and then emerge from the spinifex in their thousands.

At night the desert resonates with the songs of katydids, the loudest of which come from Robust Fan-winged Katydids (Psacadonotus robustus). Unfortunately the fat abdomen of this dun-coloured species is often host to the larvae of tachinid flies (family Tachinidae). These parasites feed on the internal organs before emerging from the katydid which dies soon afterwards.

One of our prime targets is Mitchell’s Cockroach (Polyzosteria mitchelli) which we breed at Melbourne Museum off-display, perhaps the most beautiful cockroach in Australia. With its golden markings and eggshell-blue legs, this species is one of more than 500 native cockroaches that are rarely seen by the average Australian but which are extremely important in native ecosystems. They shouldn’t be confused with the five or so introduced cockroach species that infest our houses–native cockroaches are happy in the bush and almost never come inside.

Wolf spiders are the dominant ground species, their emerald eyes shining in the torchlight. This male wolf spider (below) was seen halfway down a burrow and was difficult to distract until we discovered the source of his interest—a large female wolf spider at the bottom of the burrow.

To support our collection of almost 100 invertebrate species on display at Melbourne Museum, Live Exhibits staff must occasionally collect bugs from the wild, and some of these can hold unwanted surprises inside.

A Chalcid wasp, newly emerged from the cocoon of its host caterpillar.Image: Patrick HonanSource: Museum Victorai

At least one in every ten insect species is a parasite on other insects. In Australia this adds up to several tens of thousands of parasitic insect species, all living their lives on the outside or, more commonly the inside, of other insects. Most of these parasites are wasps and flies, and most of their hosts are butterflies, moths and beetles.

Parasitic insects usually lay their eggs directly onto or into the body of their host, but may lay eggs on a food plant in the hope that they will later be ingested by a potential host. Once inside, the parasitic larva consumes the host’s internal tissues while the host continues to go about its business. The parasite usually avoids the vital organs until the last minute – then polishes these off and finally kills its host.

Aphid ‘mummies’ – aphids that have been parasitised and glued to the leaf by Braconid wasps. When fully developed, the wasps will cut a perfectly circular hole in the back and emerge as adults.Image: Patrick HonanSource: Museum Victoria

Parasitic wasps are able to find their hosts no matter where they might hide. In order to lay eggs on its host – Sirex Wood Wasp (Sirex noctilio) – Megarhyssa (Megarhyssa nortoni) can drill through 9cm of solid wood with its ovipositor (egg-laying organ). Megarhyssa females find their hosts using infrared detectors on their antennae; the outer bark of a tree is 0.5oC warmer where a larva lies underneath.

A parasitic wasp will sometimes inject venom that paralyses the host but keeps it alive, allowing the wasp to hide it away for its offspring as a sort of living larder. A large wasp dragging a larger, paralysed, huntsman across open ground is a familiar sight during summer.

A Pompilid wasp drags a huntsman (Isopeda species) from its hiding place under bark, before paralysing it and inserting an egg.Image: Patrick HonanSource: Museum Victoria

A caterpillar can sometimes dislodge a parasite’s eggs with its mandibles, but wasps usually lay their eggs just behind the caterpillar’s head where they can’t be reached. Many hosts are able to ‘encapsulate’ a parasite already inside their bodies, localising its damage and starving it of oxygen. When more than one parasite is laid inside a host, the larvae fight to the death within the host’s body for the rights to its organs.

Thousands of parasitic wasp cocoons inside the empty shell of a Cabbage White Butterfly caterpillar (Pieris rapae). Each cocoon will soon produce a tiny wasp that flies off to find other caterpillars to parasitise.Image: Patrick HonanSource: Museum Victoria

Parasites are themselves subject to attack from hyperparasites, insects that lay eggs inside an already-occupied host. The emerging larva seeks out the parasite in residence and burrows into its body. These in turn may be parasitised by superhyperparasites, and so on.

Chauliognathus lugubris. The Plague Soldier Beetle. This wee beast accounts for hundreds of insect identification requests we receive at the Discovery Centre during the summer. At this time of year these little pollinators descend from the crowns of flowering trees to indulge in seething masses of mating activity triggered by hot weather.

This frenzied 'coupling' activity rarely goes unnoticed, especially because of the numbers in which the beetles congregate– we often get calls from people describing masses of these little cigar-shaped critters with their distinctive orange collars in their gardens; regular readers will have read our earlier post about Plague Soldier Beetles.

Last week, however, it seems this beast and its plaguing behaviour caught the attention of the Rainbow Lorikeet class at Dame Nellie Melba Kindergarten in Richmond. The Lorikeets' teacher Adam contacted us with an identification request, accompanied by some photographs and observations of the insects in question from the students, some of which I’ll share below:

As seasoned respondents to enquiries of all types from the public, we thought the Rainbow Lorikeets were particularly clever in separating their observations into 'what we think' and 'what we know' – in doing so, they were more than half-way there with their identification by the time it reached us. This, along with the photos, made our entomologist’s job quite easy in providing the identification as Plague Soldier Beetles.

The MV Library holds an important collection of 18th and 19th century scientific literature. Many of these books began as working tools for early museum curators studying the local fauna. Now, they form part of our rare book collection and are prized for their beauty and rarity.

The library's collection has an interesting history, forming from the amalgamation of two specialist collections from the National Museum of Victoria and Science Museum. Books have been purchased since the earliest days of the National Museum of Victoria, when the first director, Frederick McCoy, acquired important titles such as the entomological works of Maria Sybilla Merian.

While the library collection at MV is relatively small, it is also surprisingly unique. Library staff are currently working to identify titles unique to Australian libraries, a project which has exposed some real gems in the collection, such as John Abbot’s The Natural History of the Rarer Lepidopterous Insects of Georgia (1797).

Abbot left his native England in 1773 for the colony of Virginia in North America, in order to procure specimens and make drawings of the local insects. Following the outbreak of the American Revolutionary War in 1775, Abbot moved to Georgia, where he spent the rest of his life recording the local insects and birds.

Although he was a prolific natural history artist and well regarded in his lifetime, Abbot is not as well remembered as some of his contemporaries, who included famous naturalists such as John James Audubon. While he is thought to have created four to five thousand watercolours, most of them were unpublished or uncredited during his lifetime.

The Natural History of the Rarer Lepidopterous Insects of Georgia includes 104 hand-coloured plates by John Harris, after original artwork by John Abbot. It's an important early work to depict North American butterflies and moths, and has been appreciated by scientists and collectors alike for its accuracy as well as its beauty. The introduction was written by James Edward Smith, a founder of The Linnean Society of London.

While it is exciting to encounter rare material in our collection, it is also nice to be able to share it. Luckily, the work has been digitised and is now freely accessible through the Biodiversity Heritage Library, so have a browse online or download your own copy of this rare work!

Job, Frank, “The Library of Museum Victoria” in Rasmussen, C. (ed.), A Museum for the People: A History of Museum Victoria and its Predecessors, 1854-2000, Carlton North, Vic.: Scribe Publications, 2001.

If you're out in the bush or a local park during winter, you're likely to happen across a group of 'spitfires' clinging to the branch of a gum tree in the cold. These insects are technically called sawflies, a group of insects closely related to wasps. There are more than 200 species of sawfly in Australia, but the local species is the Steel Blue Sawfly (Perga dorsalis).

A small clutch of sawfly larvae clinging to a branch.Image: Patrick HonanSource: Museum Victoria

The name 'sawfly' derives from a 'sawbench' under the abdomen of the female with which she lays eggs. Female wasps, in contrast, use a pointed ovipositor to lay eggs and in some species this doubles as a sting – adult sawflies do not sting and both adults and larvae are completely harmless.

Female sawflies use the sawbench to cut the upper surface of a leaf and deposit 60-70 eggs into the leaf tissue. The larvae hatch and feed on gum leaves, grouping together for protection in a rosette pattern, similar to the head-outwards stance adopted by Bison when under attack. This is known as a 'ring defence', or cycloalexy. As the larvae grow, they collect in larger groups around branches during the day and spread out to feed at night.

A raft of eggs cut into a gum leaf by a female Steel Blue Sawfly.Image: Patrick HonanSource: Museum Victoria

Like their cousins, the ants, bees and wasps, sawflies show some social behaviour but only in a primitive way. When feeding at night, larvae tap the branch to keep in constant communication with each other. If an individual becomes lost, it will tap more rapidly until it receives an answer from the rest of the group – if an individual becomes completely separated it will not survive long on its own.

Sawflies grouped together on a branch. The pale tips of the abdomen are tapped on the branch to keep in touch.Image: Patrick HonanSource: Museum Victoria

The activities of a group of sawfly larvae are governed by a few select individuals that become in effect the leaders of the group. They lead the rest out to feed at night and, if they run out of food, lead the group across the ground to other trees. When large numbers of sawfly larvae are present they are able to defoliate small gum trees, but in general are not a major pest.

A mass of sawflies resting during the day, the result of the merging of several smaller groups.Image: Patrick HonanSource: Museum Victoria

When ready to pupate, the larvae leave the host tree and burrow down to make mass cocoons in the soil. Here they sit through spring and summer to emerge in early autumn. Adults have no mouthparts and do not feed, living only for a week or so.

Not all emerge, however, as many succumb to parasitic flies. These flies, about the size of a blowfly, will lay eggs in the sawfly larvae and the fly maggot literally eats its host from the inside out, eventually emerging from the sawfly's cocoon.

An opened pupal cell showing the consumed sawfly larva on the left, and the engorged parasitic fly larva on the right.Image: Patrick HonanSource: Museum Victoria

Sawfly larvae have an unusual defensive mechanism that has given them the name 'spitfires'. They store eucalyptus oil in a small sac in their gut, and regurgitate this oil when under threat. Despite their nickname, they are unable to actually spit this fluid and the oil itself is harmless unless eaten (like all eucalyptus oil). In fact it has a very pleasant eucalytpusy smell.

A large blob of frothy regurgitate in the mouthparts of a sawfly larva.Image: Patrick HonanSource: Museum Victoria

Australia is one of the main strongholds of Symphyta, the suborder of insects to which sawflies belong. The Steel Blue Sawfly is one of the few insect species active in Victoria during winter, so next time you're in the bush take the time to stop and smell the sawflies.

Some of us with a wool or wool blend carpet have had the unpleasant experience of noticing our carpets slowly receding from the wall. Closer inspection of this phenomenon shows numbers of hairy carpet beetle larvae to be the cause of the loss.

There are a number of different species of introduced and native carpet beetles. As adults carpet beetles are small and usually dark, often with patterned scales on the body. The adults feed on pollen and can often be found on the window ledge trying to get outside to feed. The larvae can often be hard to see so finding the adults on window ledges can be a good pointer as to the likely presence of the larvae. As the adults feed on pollen, they won’t cause damage to property but of course will be looking to lay more eggs to maintain the population.

Despite their common name, these tenacious insects will feed on a variety of things such as carcasses, feathers, felt, textiles of an organic nature and pet hair.

These beetles can originate in bird or mammal nesting which may be in the roof or walls from where the larvae and adults find their way down into the house. Neither the larvae nor the adult beetles bite people but if left unchecked they do have the ability to cause damage to a variety of objects containing organic matter such as carpets, felt on pianos, clothing made from wool, insect collections and animal mounts. There is also the possibility for the shed larval skins to cause some irritation to people.

While these small beetles do a great job in nature of helping to break down and consume organic matter it is wise to prevent them from dining out on your expensive woollens. Undertake regular vacuuming concentrating under furniture or areas that are not often disturbed. Keep an eye out for any build up of pet hair and lint which can also support populations of these beetles.